1. Field of the Invention
The present invention relates to a spin valve head. More particularly, the present invention relates to a spin valve head and a method of manufacturing the spin valve head capable of converting a change in a signal magnetic field, which is provided by a magnetic recording medium, into a change in electrical resistivity by the spin valve magnetic resistance effect. Also, the present invention relates to a magnetic recording and reproducing device such as a magnetic disk device or a magnetic tape device using the above spin valve head.
2. Description of the Related Art
Recently, the size of a magnetic recording and reproducing device such as a magnetic disk device has been reduced and, further, recording has been conducted at high density. Accordingly, as a reproducing head of such a device, there is provided a reproducing head using the magnetoresistive effect by which a change in the signal magnetic field provided by a magnetic recording medium is converted into a change in electrical resistivity. This reproducing head is called MR head. Especially, a GMR head, which is one type of MR head, is receiving attention because it can generate a high output without depending upon the moving speed of the magnetic recording medium. Especially, a spin valve head utilizing the spin valve magnetoresistive effect can be relatively easily manufactured, and further a rate of change of electric resistance in a low magnetic field is higher than that of other MR heads. Therefore, the spin valve head utilizing the spin valve magnetic effect has already been put into practical use.
The spin valve head, as shown in FIG. 1 as an example, includes a magnetoresistive effect film (spin valve film) 70; a pair of electrodes 68 which electrically join to the spin valve film 70 and define a signal detecting region and allow a signal detecting current to flow in the signal detecting region; and a pair of longitudinal bias magnetic field impressing layers 67 for impressing a longitudinal bias magnetic field upon the spin valve film 70. The longitudinal bias magnetic field impressing layers 67 are commonly composed of hard thin magnetic films made of CoPt or CoPtCr. When the longitudinal bias magnetic field impressing layers 67 are arranged in portions except for the magnetism sensing section (signal detecting section) of the spin valve head 71 in such a manner that the longitudinal bias magnetic field impressing layers 67 are located on both sides of the spin valve film 70 or on the spin valve film 70 (not shown in the drawing), it is possible to suppress the occurrence of Barkhausen noise caused by the movement of a magnetic wall in the free magnetic layer, which will be explained later referring to FIG. 2, of the spin valve film 70. Therefore, it is possible to obtain a stable reproduction waveform in which no noise is caused.
As shown in FIG. 2, which is a cross-sectional view taken on line IIxe2x80x94II in FIG. 1, the spin valve film 70 is composed of a regular antiferromagnetic layer 64, a pinned magnetic layer 63, which is also referred to as a stationary magnetic layer, a nonmagnetic intermediate layer (Cu layer) 62 and free magnetic layer 61, and these layers are laminated on the described order. When the above arrangement of lamination is adopted, an angle formed by the magnetizing directions of the two magnetic layers (free magnetic layer 61 and pinned magnetic layer 63) which are laminated via the nonmagnetic intermediate layer 62 can be adjusted. In this way, electric resistance can be changed into a desired value.
In order to provide a spin valve head in which Barkhausen noise is not generated and the fluctuation of reproduction characteristic is small, Japanese Unexamined Patent Publication (Kokai) No. 9-97409 discloses the following arrangement. The longitudinal bias magnetic field impressing layer, which has been explained above referring to FIG. 1, includes: a ferromagnetic thin film, the crystal structure of which is a body-centered cubic lattice; an underlayer film which is an amorphous ferromagnetic thin film or an antiferromagnetic thin film, the crystal structure of which is a body-centered cubic lattice; and a hard magnetic thin film formed on the underlayer film.
As proposed by Japanese Unexamined Patent Publication (Kokai) No. 9-97409, in the structure in which the hard magnetic thin film is arranged on both sides of the spin valve film, a magnetic exchange coupling is generated between the spin valve film and the hard magnetic thin film by using the ferromagnetic thin film as the underlayer of the hard magnetic thin film, which is effective as a means for suppressing the occurrence of Barkhausen noise. However, this structure is disadvantageous as follows. In this structure, the magnetic exchange coupling generated between the spin valve film and the hard magnetic thin film is limited to a portion in which both end portions of the spin valve film are tapered, that is, the magnetic exchange coupling generated between the spin valve film and the hard magnetic thin film is limited to a very small joining portion which is called xe2x80x9can abutted junctionxe2x80x9d. A profile of this joining portion is affected by the process of formation of the spin valve film, that is, a profile of this joining portion is affected by the photolithographic method, the ion milling method or the process of forming a hard magnetic thin film. Accordingly, it is difficult to form the joining portion into the same profile without causing any fluctuation. If the profile of the joining portion fluctuates, the magnetic exchange coupling also fluctuates. Further, the hard magnetic thin film activates a bias magnetic field on the spin valve film, and the magnetic field sensitivity at both ends of the signal detecting region is deteriorated.
It is a first object of the present invention to provide a spin valve head characterized in that the abutted junction region is extended so as to cause the magnetic exchange coupling in a wider area, so that the occurrence of Barkhausen noise can be more effectively suppressed and the abutted junction region can be stably formed without being affected by the process of formation of the spin valve film or hard magnetic thin film, so that reliability of the magnetic exchange coupling can be enhanced and deterioration of the magnetic field sensitivity at both ends of the signal detecting region can be prevented.
It is a second object of the present invention to provide a method of manufacturing the above spin valve head easily without it being affected by the formation process.
It is a third object of the present invention to provide a magnetic disk device having the spin valve head of the present invention.
These objects and other objects of the present invention will be more easily understood by the following detailed explanations.
The present inventors have found that the above problems of the prior art can be solved by providing a spin valve head comprising:
a spin valve film containing a regular antiferromagnetic layer, a pinned magnetic layer, an intermediate layer and a free magnetic layer which are laminated in the above order;
a pair of electrodes arranged at both ends of the spin valve film, electrically connected with the spin valve film so as to define a signal detection region and apply a signal detection current flow to the signal detection region; and
a pair of exchange bias magnetic field impressing layers arranged at both ends of the free magnetic layer of the spin valve film, magnetically exchange coupled with the free magnetic layer so as to impress an exchange bias magnetic field for controlling a magnetic domain upon the free magnetic layer,
wherein the exchange bias magnetic field impressing layers are made of antiferromagnetic material, and the spin valve film extends onto the exchange bias magnetic field impressing layers.
In the spin valve head of the present invention, it is preferred that the exchange bias magnetic field impressing layer is made of antiferromagnetic material such as PtMn, PdPtMn, NiMn, CrMn, CrPtMn, RuMn, RuRhMn, IrMn, IrRhMn or IrRuMn and that the uppermost layer is covered with NiFe which is a portion of the free magnetic layer of the spin valve film.
When the spin valve head is composed as described above, the area of a portion in which the magnetic exchange coupling is caused between the spin valve film and the exchange bias magnetic field impressing layer can be remarkably increased. Therefore, fluctuation of the magnetic exchange coupling described before can be remarkably suppressed. Accordingly, controlling of the magnetic domain of the spin valve film can be more stably conducted by the exchange bias magnetic field impressing layer. Therefore, the generation of Barkhausen noise can be effectively suppressed.
When Ta or other appropriate metals are made to exist as a common underlayer between the spin valve film and the exchange bias magnetic field impressing layer, the free magnetic layer can be formed under the condition of good crystallization even in the case of the longitudinal bias under-lay type spin valve head of the present invention, that is, it is possible to form a free magnetic layer, the soft magnetic characteristic of which is excellent.
In addition to the above excellent spin valve head, the present inventors have invented a method of manufacturing the spin valve head according to the present invention and a magnetic disk device comprising the spin valve head according to the present invention.